Contact system for a high-voltage apparatus

ABSTRACT

A contact system for an electrical high-voltage apparatus or the like such as a high-voltage power circuit breaker or the like wherein a gaseous insulating medium is used includes a contact system having at least one contact piece. The contact piece includes an electrically conductive annular member having respective end portions. One of the end portions carries a graphite electrode having a nozzle-like configuration for conducting away the gases produced when the apparatus is switched to the open position. The contact piece is also provided with support member having a free end portion. The other end-portion of the annular member surrounds and engages the free end-portion of the support member to form a shrink-joint therewith and thereby establishes a good electrical connection between these members.

United States Patent 1191 Rolff CONTACT SYSTEM FOR A HIGH-VOLTAGE APPARATUS 1 Mar. 25, 1975 207,l27 12/1939 Switzerland ..20()/l48R 75 l t Kl t R m B Primary Examiner-Robert S. Macon 1 nven or aus e er 0 er m Germany Attorney, Agent, or FirmKenyon & Kenyon Reilly [73] Assignee: Siemens Aktiengesellschaft, Munich, C & Ch pin Germany [22] Filed: June 4, 1973 [57] ABSTRACT [21] App]. No.: 366,295 A contact system for an electrical high-voltage apparatus or the like such as a high-voltage power circuit breaker or the like wherein a gaseous insulating me- [330] Forelgn Application Pnomy Data dium is used includes a contact system having at least June 1972 Germany 2232314 one contact piece. The contact piece includes an electrically conductive annular member having respective [52] US. (,l. 200/148 R, 200/146 R end portions o of the end portions Carries a graph [51] int. Cl. H6lh 33/82 ite electrode having a nOZZkHike Configuration for Fleld 0f Search R, G, D, d ti away the gases produced when the appara- 200/146 R tus is switched to the open position. The contact piece is also provided with support member having a free [56] References C'ted end portion. The other end-portion of the annular UNITED STATES PATENTS member surrounds and engages the free end-portion 2.364.981 12 1944 Journeaux 200/146 R of th upp rt m mber to form a shrink-joim there- 3 789.l75 1/1974 Beier et al ZOO/I48 R with and thereby establishes a good electrical connec- FOREIGN PATENTS OR APPLICATIONS between these members- 525244 8/1940 United Kingdom 200/148 G 6 Claims, 2 Drawing Figures oh. W;

CONTACT SYSTEM FOR A HIGH-VOLTAGE APPARATUS BACKGROUND OF THE INVENTION The invention relates to an electrical high-voltage ap paratus, and in particular, high-voltage circuit breakers of the kind disclosed in Deutsche Auslegeschrift 1,154,548 for example. The electric circuit breaker disclosed in this publication operates with an electronegative, fluorine-containing gas as the quenching and insulating medium and includes two contact pieces which are movable relative to each other and across which an arc is drawn when the breaker is opened. The contact pieces are made of carbon, preferably graphite, in order to keep the destruction of the contact pieces and the formation of decomposition products low under the action of the are. The contact pieces consist ing of graphite are solid and are inserted into cupshaped electrodes. The walls of the cup-shaped electrodes engage at least partially in undercuts on the periphery of the contact pieces to achieve a secure mechanical and electrical connection.

SUMMARY OF THE INVENTION The contact system according to the invention can be utilized in a high voltage apparatus. Each electrode of the contact system is advantageously configured in the shape of a nozzle for the removal of switching gases. The electrode is surrounded and engaged by an electrically conductive annular member and forms therewith a friction fit. It is thereby possible to mount the nozzleshaped graphite in a mechanically stable manner so as to preclude breakage thereof. The annular member is an intermediate member and carries the current flowing through the breaker as well as the arc current produced when the circuit is interrupted during the opening operation.

The annular member can in turn be connected to a corresponding contact piece support member in an electrically conducting manner.

It is an object of the invention to provide a contact system which includes at least one contact piece wherein a good mechanical and electrical connection is provided between the support member of the contact piece and the annular member which carries the graphite electrode.

The invention provides a contact system having an improved electrical connection between the annular member and the contact piece support member. According to a feature of the invention, a shrink-joint is provided between the annular member and the free end-portion of the contact support member. One endportion of the annular member carries the graphite electrode whereas, the other end-portion of the same member surrounds and engages free end-portion of the contact piece support member to form the shrink-joint therewith thereby establishing a good electrical connection between the members.

Such a shrink-joint is able to withstand the high stresses produced by the temperature cycles such as occur in modern highvoltage power circuit breakers better than a threaded connection. In addition, it is possible to configure the shrink-joint so that the commutation ofa movable contact member to the annular member and also to the graphite electrode is improved, the

movable contact member sliding off ol' the contact piece during the breaker opening operation.

In a preferred embodiment of the invention, the annular member engages in a ring-shaped recess formed in the outer surface of the contact piece support member. To particular advantage, the outside diameters of the annular member and the contact piece support member beyond the region of the joint are equal to each other; this arrangement simplifies the movement of the bridging contact member which is highly stressed during the breaker opening operation.

Improved commutation at the points at which the annular member butt joins the contact piece support member and at which a discontinuity of the electric conductivity results because of the difference in material composition of the annular member and the contact piece support member can be achieved if respective outer surfaces of the annular member and the contact piece support member are tightly joined together.

In a preferred embodiment of the contact system of the invention, the graphite electrode projects axially out from the annular member. The outer diameter of the electrode is the same as the respective outerv diameters of the annular member and the contact piece support member. With this outer diameter, the electrode joins tightly with the annular member at the outer surface thereof. When the contact system of the invention is incorporated in high voltage power circuit breakers of the highest capacity, the annular member is preferably made of a metal consisting largely of iron; whereas, the contact piece support member is made of copper.

Although the invention is illustrated and described herein as contact system for a high-voltage apparatus, it is nevertheless not intended to be limited to the details shown, since various modifications may be made therein within the scope and the range of the claims. The invention, however, together with additional objects and advantages will be best understood from the following description and in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates the contact system according to the invention. The contact system is shown disposed in the switching chamber of an electric high-voltage circuit breaker. The right half of the drawing to the right of the center line shows the movable bridging member in a position corresponding to the closed position of the breaker, and in the left half, the bridging member is shown for the open position of the breaker.

FIG. 2 is an exploded view of one contact piece of the contact system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. I, the switching chamber 10 can consist, for instance, of porcelain and can contain a gaseous insulating medium such as sulfur hexafluoride. In the interior 12 of the switching chamber 10, two contact pieces 1 are arranged having mutually adjacent end-face portions. The contact pieces I carry respective graphite electrodes 6 at the end-face portions by means of an electrically conductive member 4. The graphite electrode is of nozzle-shaped configuration and directs away the hot switching gases which are produced during the time that the arc burns. These switching gases are passed onthrough the interior of the hollow contact pieces.

To the right of the centerlinc, the bridging contact member 11 is shown in a position which corresponds to the closed position of the circucit breaker. In the closed position, the two contact pieces I are connected with each other in an electrically conducting manner by a bridging contact member 11. In the open position of the breaker, the gap between the two contact pieces 1 is cleared by the bridging contact member which was moved in the direction of the arrow.

FIG. 2 is an exploded view of one of the contact pieces 1 shown in FIG. 1. The contact piece is made hollow for the removal of the switching gases produced during the breaker opening operation. The gaseous insulating medium used such as sulfur hexafluoridc serves at the same time as the quenching medium when the contact system is part of an electrical high-voltage apparatus such as a high-voltage power circuit breaker. This quenching medium is conducted to the gap under a predetermined pressure when the breaker is switched to the open position and is removed from the gap through the hollow contact pieces 1. Such a predeter mined pressure can be 16 bar for example.

The contact piece support member 1A has a ringshaped recess 3 in the region 2 of its end-face portion which receives the electrically conducting ring-shaped member 4. The inside diameter d of the ring-shaped member 4 is smaller than the outside diameter D of the recessed region of the contact piece support member 1A at the end-face portion thereof. For establishing the shrink joint between the ring-shaped member 4 and the contact piece support member 1A, the latter can be undercooled while the ring-shaped member 4 is kept at room temperature. The cooling of the support member 1A can, for example, take place in liquid air. Further, the inside diameter d of the ring-shaped member 4 is smaller than the outside diameter D of the recessed region of the graphite electrode 6, so that also between the graphite electrode 6 and the ring-shaped member 4 a friction fit can be established. The joining of the parts 1A, 4 and 6 can take place in a single operation.

As shown in FIG. 2, the outside diameters D D and D of the parts 1A, 4 and 6 are the same. Through the choice of shrink joints between the parts, it is possible to join the outer surfaces of the parts 1A, 4 and 6 tightly together.

It is possible to make the electrically conductive ringshaped member 4 of a metal consisting largely of iron with C between 0.07 and 0.15 p.c.; Si between 0.10 and 0.30 p.c.; Mn between 0.30 and 0.55 p.c.; P no more than 0.05 p.c. and S no more than0,05 p.c.

In a somewhat different embodiment, the ringshaped member 4 can consist of metal which is 36% nickel and the rest iron. in a still further embodiment, the ring-shaped member 4 can consist of a metal with 28% nickel, 18% cobalt and the rest iron. in all embodiments, copper is chosen as the material for the contact piece support member 1A.

The invention affords a good mechanical contact and an improved electrical contact between the ringshaped member 4 and the support member 1A; this good electrical and mechanical contact between members 1A and 4 is maintained also under the stress produced by hightemperature changes.

The ring-shaped member 4 can be arranged so that it receives, on the side supporting the graphite clcctrodc, an azimuthal stress coming close to its elastic limit at a temperature of 40C; whereas, the graphite electrode is stressed at its inner edge up to the maximum compression strength of the graphite material. At

1 temperatures above 40C, the different thermal expansions between the ring-shaped member 4 and the graphite electrode is compensated by elastic deformation.

The side of the ring-shaped member 4 facing the contact piece support member 1A can be given such dimensions that at the highest operating temperature (for example +l20C), the ring-shaped member 4 receives an azimuthal stress approaching its elastic limit. The contact pressure is preferably chosen so that also the contact piece support member 1A is stressed up to the elastic limit of the copper material in the region of the joint.

What is claimed is:

l. A contact system for an electrical high-voltage apparatus such as a high-voltage power circuit breaker or the like wherein a gaseous insulating medium is used, the contact system comprising at least one contact piece that includes a graphite electrode having a nozzle-like configuration for conducting away the gases produced when the apparatus is switched to the open position, an electrically conductive annular member having respective end-portions, said electrode being held in surrounding engagement by one of said endportions of said annular member in a friction-tight manner, and a contact piece support member having a free end-portion, the other end-portion of said annular member surrounding and engaging said free endportion of said support member to form a shrink joint therewith thereby establishing a good electrical connection between said members as well as a good mechanical connection for withstanding temperature changes occurring in the apparatus.

2. The contact system according to claim 1, said free end-portion of said support member having an open ring-shaped recess formed in the outer surface thereof, said other end portion of said annular member surrounding and engaging said free end-portion in said recess thereof.

- 3. The contact system according to claim I, said annular member and said contact piece support member having respective outer diameters beyond the region of said shrink joint, said diameters being equal to each other.

4. The contact system of claim 1, said annular member and said contact piece support member being mutually joined at said shrink joint so as to cause the outer surface of said support member beyond said free endportion to tightly abut the outer surface of said annular member.

5. The contact system of claim 4, the graphite electrode projecting axially from said annular member and having an outer diameter equal to the outer diameters of said annular member and said support member, the outside surface of said electrode being tightly adjacent the outside surface of said annular member.

6. The contact system of claim I, said annular member being of a metal consisting largely of iron, and said annular member being made of copper. 

1. A contact system for an electrical high-voltage apparatus such as a high-voltage power circuit breaker or the like wherein a gaseous insulating medium is used, the contact system comprising at least one contact piece that includes a graphite electrode having a nozzle-like configuration for conducting away the gases produced when the apparatus is switched to the open position, an electrically conductive annular member having respective end-portions, said electrode being held in surrounding engagement by one of said end-portions of said annular member in a friction-tight manner, and a contact piece support member having a free end-portion, the other end-portion of said annular member surrounding and engaging said free end-portion of said support member to form a shrink joint therewith thereby establishing a good electrical connection between said members as well as a good mechanical connection for withstanding temperature changes occurring in the apparatus.
 2. The contact system according to claim 1, said free end-portion of said support member having an open ring-shaped recess formed in the outer surface thereof, said other end portion of said annular member surrounding and engaging said free end-portion in said recess thereof.
 3. The contact system according to claim 1, said annular member and said contact piece support member having respective outer diameters beyond the region of said shrink joint, said diameters being equal to each other.
 4. The contact system of claim 1, said annular member and said contact piece support member being mutually joined at said shrink joint so as to cause the outer surface of said support member beyond said free end-portion to tightly abut the outer surface of said annular member.
 5. The contact system of claim 4, the graphite electrode projecting axially from said annular member and having an outer diameter equal to the outer diameters of said annular member and said support member, the outside surface of said electrode being tightly adjacent the outside surface of said annular member.
 6. The contact system of claim 1, said annular member being of a metal consisting largely of iron, and said annular member being made of copper. 